In video conferencing systems, it can be desirable to provide a system that moves the camera so that the view of the camera changes as the speaker changes. In general, there are several conventional methods used to accomplish such camera movement, including automated camera tracking and camera preset methods.
One automatic tracking method employed in conventional video conferencing systems uses infrared (IR) and radio frequency (RF) technology. This conventional method uses a transmitter, carried by the speaker, and IR and RF receivers to triangulate the position of the transmitter. By using the IR and RF signals to compute a new position of the speaker and making appropriate changes in camera position, the camera can be moved to track the speaker. However, this type of system does not work well in a conference room environment where a number of persons may talk.
Some conventional systems use a camera preset method for tracking the camera to the speaker. In general, a "camera preset" is a set of control values for the camera that correspond to a particular view of the camera. A "camera preset location" is a point in space that is viewed by the camera when the camera is positioned according to a given camera preset. For example, a camera preset location can be a point in a conference room where it is expected that a speaker will be positioned, and the camera preset stores control values for making the camera view that position. Where the camera is a pan, tilt, zoom (PTZ) camera, the camera preset can include a value for each of the three parameters (pan, tilt, and zoom) that would control the view of the camera such that it views the camera preset location.
One conventional method for selecting a camera preset is a centralized preset device. In this method, each camera preset is associated with a button on a centralized control device. An operator can press the button associated with a particular camera preset when the operator desires the camera to view the associated camera preset location. In this manner, the operator can manually track the speaker by knowing the camera preset locations for each camera preset. This preset selection system suffers from its reliance on the operator, who can be slow to react or can forget to react. Furthermore, the number of camera presets is limited to the number of buttons on the centralized device.
Another conventional method is the use of a touch-to-talk microphone. This method associates each camera preset with each of a number of touch-to-talk microphones. When a user pushes the button to activate his microphone, the camera preset associated with that microphone is selected. The camera is then moved to view the camera preset location for that camera preset (which, if set-up correctly, should view the speaker).
There are several problems with the touch-to-talk microphone method. First, the number of functional camera presets is limited to the number of microphones available. Second, a speaker may forget to touch the microphone before speaking. Third, if more than one person presses the button on their touch-to-talk microphone, the camera will thresh between the two camera presets before settling. Also, after a video conferencing system is set up, it can be costly to add additional camera presets.
Use of a voice activated microphone is a variation of the press-to-talk microphone method. A voice activated system differs from the touch-to-talk system in that a user is not required to press a button to activate his microphone and cause selection of the camera preset associated with his microphone. The microphone recognizes when someone talks into it and activates itself. Once a microphone is activated, the camera preset for that microphone is selected. This method also has a number of problems, including limitations on the number of camera presets and the costs of adding additional camera presets.
A further conventional method for selecting camera presets uses an infrared transmitter having a button that the user can press. The transmitter signals that the button has been pressed, and the camera is moved to view the camera preset location associated with that infrared transmitter. This is a slight modification of the touch-to-talk microphone, and the associated problems of the touch-to-talk microphone are not solved.